In the communications industry it is commonplace for two cables to be connected at one or more splice locations. Typically, each cable comprises a multitude of individual conductors which must be spliced to join the cables. It has been estimated that over two billion splice connections are made each year in the telephone industry, with the labor costs alone being staggering. It is obviously important for these splice connections that they be durable and, preferably, permanent so that the need for replacement splices is minimized.
Typically, the individual conductor ends to be spliced are brought and held together in multiple contact connectors such as one which is disclosed in U.S. Pat. No. 3,858,158 to Henn et al., the disclosure of which is incorporated herein by reference. To protect the spliced conductors, the connector is commonly packed with a filling compound which is meant to prevent the conductors from contacting or being contacted by water and other contaminants, inasmuch as exposure of spliced conductors to water and other contaminants lowers the lifetime of the connections by causing deterioration and corrosion of the connector, its filling compound and the conductors. Not only is the capacitance balance of transmission lines and hence the electrical performance upset by such exposure but also serious corrosion may occur and telephone company personnel are forced to spend many hours at considerable expense repairing lines and restoring telephone service following such damage to connectors and conductors. These filling compounds have been shown to be, at times, inadequately. protective of the individual conductors and spliced ends against corrosion, and the filling compound itself oftentimes becomes contaminated from contact with water, fungus, insects, insect droppings, dust, dirt and other contaminants. In addition, it is not always desirable to add filling compound to the connector. For example, adding filling compound raises the manufacturing costs of the connector and hence the cost of splicing.
Thus, it is apparent that a method and/or material for preventing contamination and corrosion of multiple conductor connectors is needed, which will protect the connector and conductors even if filling compound is not present and will protect the filling compound as well, if it is present. One technique which has been developed to decrease the contamination of the filling compound and corrosion of the conductors is the inclusion of a fungicide and corrosion inhibitor in the filling compound, as taught in a co-pending patent application, Ser. No. 08/489,423 to Bair et al., filed Jun. 12, 1995.
A technique for use in protection of the spliced portions of an optical fiber is taught by Murata et al. in U.S. Pat. No. 4,509,820, and involves wrapping the fiber in a heat shrinkable polymeric tube capable of shrinking in the radial direction. The heat shrinkable tube is then heated by application of an electrical resistance heating element, whereupon the heat shrink material shrinks and forms a protective coating around the optical fiber. This simple technique would not work for connectors because the many conductors connected to the connector would get in the way and would not allow the film to adequately cover the connector.
Heat shrinkable thermoplastic films have been used for various applications, probably most typically for packaging of food products such as meat, cheese, poultry and the like. A heat shrinkable film is a film that is stretched and oriented while it is being cooled so that later, when used for packaging, it will, upon being rewarmed, shrink tightly around the package contents. Blown film made from plasticized polyvinylchloride (PVC) is the most widely used heat shrink film. Other commonly used thermoplastics are polyethylenes and polypropylenes. The manufacture of a single layer heat shrink film may generally be accomplished by extrusion of a thermoplastic resinous material which has been heated to or above its flow or melting point from an extrusion die in, for example, either tubular or planar (sheet) form, followed by postextrusion cooling. The stretching or orienting of the film may be conducted at some point during the cool-down while the film is still hot and at a temperature within its orientation temperature range, followed by completion of the cooling. Alternatively, after the postextrusion cooling, the relatively thick extrudate is then reheated to a temperature within its orientation temperature range and stretched to orient or align the crystallites and/or molecules of the material, and then cooled again.
The heat shrink film may then be formed into a pouch or bag, perhaps utilizing an appropriate adhesive, and the product inserted into the pouch or bag. Alternatively, a sheet of the material may be utilized to overwrap the product. The enclosed product is then subjected to elevated temperatures, for example, by passing the enclosed product through a hot air tunnel or by placing it in hot water. This causes the enclosing heat shrinkable film to shrink around the product to produce a tight wrapping that closely conforms to the contours thereof. Such packaging methods, and others, are well known to those of skill in the art.
The above general outline for manufacturing heat shrink films is not meant to be all-inclusive and other such processes are well known to those in the art. For example, see U.S. Pat. Nos. 4,274,900, 4,299,241, 4,194,039, 4,188,443, 4,048,428, 3,821,182, 3,022,543 and 5,079,051. The disclosures of these patents are generally representative of such processes and are hereby incorporated by reference.
As is apparent from the foregoing discussion, it is a problem in the industry that spliced cable connectors are oftentimes contaminated by exposure to water, dirt dust, fungus, insects, and other contaminants. Contamination is certain to occur in connectors that contain filling compound, inasmuch as the compound is greasy and is readily contaminated with dirt, insects, insect droppings, etc. These contaminants then migrate through the filing compound, contact the metal surfaces and cause corrosion. This contamination is, eventually, likely to cause decay of the filling compound and corrosion of the conductors. Loss of telephone service will result along with the need for expensive repair by the telephone company. The present invention is a way to avoid such problems by protectively wrapping the connector and thus eliminating contact with contaminants. The wrap is a barrier that prevents contaminants from contacting the surface of the sticky filling compound.